With mobile electrical devices being more and more popular in our daily life, their power supply has inevitably become one important concern. Currently, lithium secondary batteries are being widely adopted, while high demands with regard to the electrical and mechanical properties thereof shall be satisfied. For instance, small, lightweight secondary batteries with high capacity and high cycling stability are highly welcomed for the purpose of achieving both portability and long lifetime. At the same time, in the development of novel batteries, there is always an interest in being able to produce those batteries in an inexpensive manner.
Nowadays, sulfur has drawn people's attention for being used as cathode active material in lithium secondary batteries. By virtue of the low atomic weight of lithium and moderate weight of sulfur, Li—S batteries are relatively light, which are very promising in succeeding lithium-ion cells because of their higher energy density and the low cost of sulfur.
In order to achieve high-energy-density Li—S battery, many optimized categories of cathode technology and Li metal technology have been carried out to improve its electrochemical performances. Several problems need to be solved before sulfur cathode materials can be devoted to markets in rechargeable lithium batteries: (1) suitable particle size of sulfur should be achieved to ensure a high utilization rate of sulfur and then a high reversible capacity upon cycling; (2) discharge products of poly-sulfides should be carefully restrained from dissolving into the electrolyte to ensure a long cycle life; (3) the cathode material should have high ionic and electronic conductivities to ensure better rate performances.
So far, no lithium secondary battery with sulfur contained in its cathode material have yet truly succeeded in the market place due to various unsolved issues.